Teens engage in a lot of dangerous behavior that has adults wondering if they give any thought at all to the risk they're taking. After reviewing studies of adolescent behavior, Cornell University psychologist Valerie F. Reyna says they do think about it… and decide the risk is worth it. "Not only are teenagers processing risk information and weighing it rationally against benefits," she notes, "they're over-estimating those risks, and this combination leads to risk-taking behavior because the benefits for them, from their point of view, outweigh the risks."

The benefits of smoking or drinking or having sex are immediate: peer acceptance, physical pleasure. But they're also short-term. Reyna, who serves as co-director of Cornell's Center for Behavioral Economics and Decision Research, says part of the reason teens reach the conclusions they do is that they perceive situations differently than adults.

This widely divergent thought process is obvious in imaging studies comparing the adolescent and adult brains. In one study, for example, the subject were asked questions like, Is it a good idea to swim with sharks? Is it a good idea to set your hair on fire? Reyna says researchers saw the difference immediately. "It turns out that the adolescent brain - more of it lights up - they're thinking about this, they take longer to respond than adults do." She says adults don't think about all the different reasons why that might be a good idea. "It's just obvious immediately that that would be a really terrible idea."

Once teens start thinking deliberatively about the risks associated with a certain behavior, they have subconsciously accepted that it is something they might do, and that leads to risk-taking.

Reyna says rather than emphasizing the risks, parents and teachers should focus on getting teens to recognize what she calls the bottom-line cues of a situation. "They're thinking logically and they're thinking about the details. We want them to ignore the irrelevant details and focus in on the key thing: the driver is drunk, don't get in the car! It doesn't matter that this person has never had an accident, it doesn't matter that you're only going a couple blocks. These are all logical arguments, mind you, but the only thing that matters is the driver is impaired and thinking about the details can only distract you from the key bottom line there."

In other words, if it sounds like a bad idea, it probably is. But Valerie Reyna admits recognizing that concept, intuitively, might be a lesson that comes only with a few more years of life experience. Her findings appear in the journal Psychological Science in the Public Interest.